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Abstract

A two-axis scanning catheter was developed for 3D endoscopic imaging with spectral domain optical coherence tomography (SD-OCT). The catheter incorporates a micro-mirror scanner implemented with microelectromechanical systems (MEMS) technology: the micro-mirror is mounted on a two-axis gimbal comprised of folded flexure hinges and is actuated by magnetic field. The scanner can run either statically in both axes or at the resonant frequency (>=350Hz) for the fast axis. The assembled catheter has an outer diameter of 2.8 mm and a rigid part of 12 mm in length. Its scanning range is ±20° in optical angle in both axes with low voltages (1~3V), resulting in a scannable length of approximately 1 mm at the surface in both axes, even with the small catheter size. The catheter was incorporated with a multi-functional SD-OCT system for 3D endoscopic imaging. Both intensity and polarization-sensitive images could be acquired simultaneously at 18.5K axial scans/s. In vivo 3D images of human fingertips and oral cavity tissue are presented as a demonstration.

Figures (6)

Fig. 1. The MEMS mirror scanner (a) and a SEM picture of a supporting folded flexure (b). A micro-mirror is supported by a 2-axis gimbal structure composed of folded flexure hinges and can deflect in two orthogonal axes: inner and outer axis depicted in the picture.

Fig. 3. Catheter schematic (a) and photograph (b). Light path is drawn in red in the schematic and light is redirected by the MEMS scanner. The catheter photograph was taken with a ruler underneath with millimeter unit. The optical fiber is glued to the catheter body with UV curing epoxy. The MEMS scanner appears in the photograph refracted by the plano-convex cylindrical window.

Fig. 6. Movie of cross-sectional images of internal oral cavity in-vivo. Intensity image (a) and polarization sensitive (PS) image (b) are updated with the cross-section advancing in the orthogonal axis. The intensity image shows layered structures of epithelium and glands from superficial to deep, and the PS image shows no birefringence in the epithelium and some birefringence in the glands [Media 1]